煤气化装置高氨氮废水处理工艺优化与改造

Optimization of High Ammonia Nitrogen Wastewater Treatment in Coal Gasification Unit

煤气化过程产生大量的高氨氮废水,废水中氨氮化合物、硫化物含量均很高,对后续生化废水处理造成很大压力,并导致装置总排出口的总氨氮含量超标,影响装置的长周期运行。文章在某煤化工企业原有工艺的基础上,利用汽提原理对装置中气化、变换工段高氨氮废水处理工艺进行了集成优化和改造,采用了双塔加压汽提工艺,通过新增脱酸塔、脱氨塔及相应的二级分凝系统,有效降低了废水中的氨和酸性气的含量,废水中氨通过新增氨回收塔副产10%~15%(w)的氨水,可直接作为烟气脱硫的还原剂,同时新增水回收塔提高装置操作的灵活性。结果表明,该工艺可使装置内氨含量降至100μg/g,无需外供热源,同时将系统中氨进行了资源化回收,具有较好的节能效果和经济效益。

A large amount of high ammonia-nitrogen wastewater is produced in coal gasification unit. The ultrahigh concentration of ammonia-nitrogen and sulfur compounds in the wastewater makes serious impact on the following biochemical treatment, leading to excessive total ammonia-nitrogen discharge at unit outlet, which affects the long-term operation. Based on the original process in a coal chemical company and with stripping method, high ammonia-nitrogen wastewater treatment system in the gasification and conversion sections in the unit has been optimized and revamped to effectively reduce the ammonia and acidic gas contents in the wastewater, by adopting two-tower pressurized stripping process, and adding deacidification tower, deammoniation tower and compatible two-stage condensation section. The ammonia in the wastewater going through the newly-added ammonia-recovery tower comes out the byproduct ammonia water （10%- 15%）, a ＂drop-in＂ reducing agent for flue gas desulfurization. The operating flexibility is improved by adding water-recovery tower. The results indicate that these measures can reduce ammonia content in the unit to 100 μg/g, no external steam is needed, and the ammonia can be recycled, achieving good energy saving and economic benefits.